While I expect we might hear more about them at the game systems panel tomorrow (or not - we might just have to wait for the beta patch notes,) part of the Demon Hunter Starting Experience was available to play at Blizzcon. Over at WoWHead, they have a rundown of what they could try out.
Fury will be the primary resource for Demon Hunters. It appears that this will work a bit like Rage mixed with Demonic Fury - you'll generate it from abilities and spend it on other abilities, but probably without the randomness of auto-attacks.
Havoc was the spec available for play, but there were some hints at Vengeance thanks to the "Specialization" panel on the Talents/Specializations window.
DHs will get talents at 99, 100, 102, 104, 106, 108 and 110, presumably so that you won't be overwhelmed with a ton of talents right at the start.
Demon's Bite looks like a primary Fury generator, doing physical damage and generating 20-30 Fury (this might be where the randomness comes from.)
Spectral Sight slows you down but allows you to see invisible/stealthed targets near you. I assume this is toggled.
Glide allows you to reduce your falling speed by jumping midair.
Double Jump occurs if you hit jump again at the apex of your first jump - I guess you'll need to time it so you don't just glide.
Shattered Souls looks like a passive that helps keep you up when soloing. If you kill a target that yields experience or honor, they'll leave a soul fragment behind that will heal you if you run into it. If it's a demon soul fragment, you'll also get a damage boost for a few seconds!
Throw Glaive looks to work a lot like Avenger's Shield, hitting a target and bouncing between up to two additional enemies. Looks very much like a good tank pulling ability.
There were four abilities listed for each specialization on their spec pages:
Fel Rush has you charge forward, doing fire damage to anything in your path. 2 charges (on a 10 sec recharge) but no cost, apparently.
Chaos Strike is a Fury-spender that does Chaos damage to the target and is free if it crits, but otherwise costs 40 Fury.
Chaos Nova is a one-minute cooldown aoe damage burst with stun. 30 Fury.
Metamorphosis (Havoc) has you leap up and land, dealing damage and stunning enemies around you for three seconds, then transforming into a demon for 30 seconds, gaining 100% Leech and empowering Demon's Bite and Chaos Strike (not sure how.) This has a whopping ten-minute cooldown, which I hope can be reduced by various attacks or something, because it'd be sad to only be able to use this once per fight.
First off, it appears that Vengenace will have a resource called Pain - whether this replaces Fury or supplements it, I'm not sure.
Hateful Strike deals physical damage, but does more as the target's health gets lower.
Fel Blood "redirects 40% of damage taken to Fury" which suggests that you'll retain Fury as a resource. This has a 15 minute cooldown, which I don't even know what to do with.
Voidblade costs 65 Fury and deals shadow damage and then heals you for 100% of the damage done.
Metamorphosis (Vengeance) transforms you into demon form, gives you max health and Fury, and reduces damage by up to 60% - reducing more damage the lower on health you are. This has a far more reasonable 2 minute cooldown and lasts 15 seconds, which I think means it's going to be one of your major tanking cooldowns.
So far there's only one talent row. We don't know that this is also what Vengeance gets - it may very well only be for Havoc, as Vengeance was not yet playable.
Fel Fury increases damage done by Fel Rush and generates 25 Fury when Fel Rush hits at least one target (so yeah, that's got to be Havoc only)
Blade Dance is a 50 fury, 10-second cooldown ability that is a burst of aoe damage and then increases your dodge by 100% for one second.
Vengeful Retreat is an AoE attack that slows targets and has you leap away backward from them.
DHs will get a Felsaber mount, which looks like a kind of cross between a Nightsaber and a Felhound - a kind of skeletal head glowing with fel energy, but still with, you know, like, eyes.
This is still not really the full picture we need to figure out the class, but it's a nice start. I really wonder how Pain will work as a resource. I kind of get the impression that Vengeance will see a pretty bouncy health bar, a bit like Blood Death Knights, as they seem to get better at defending themselves the lower health they have.